This study concerns specific reactions which occur in the metabolism of aromatic (benzenoid, phenylpropanoid) natural products. The conversion of L-tryosine to the cyanogenic glucoside dhurrin (p-hydroxy-mandelonitrile-beta-D-glucopyranoside) in sorghum plants involves an oxime, nitrile, and a cyanohydrin. These intermediates are sequentially produced by a microsomal fraction which carries out the N-hydroxylation of L-tyrosine to form, ultimately, p-hydroxyphenylacetaldoxime. The microsomes also catalyze the beta-hydroxylation of p-hydroxyphenylacetonitrile. Both hydroxylations will be examined in detail. The cellular origin of the particles which contain these hydroxylases will be investigated to ascertain if they arise from the endoplasmic reticulum or from another membranous structure. The 2-hydroxylation of cinnamic acid catalyzed by chloroplasts from sweet clover will be examined. We will characterize this monooxygenase in detail in order to compare its properties with other, more extensively studied monooxygenases from animals and bacteria. The subsequent 4-hydroxylation of o-hydroxy-cinnamic to form 2,4-dihydroxycinnamic acid in clover chloroplasts will be examined to determine the nature of the enzyme involved. The occurrence of phenylalanine ammonia lyase in sweet clover chloroplasts will be examined to see if this enzyme is the one which is lacking in clover plants which lack the "Cu"-allele and cannot synthesize coumarin.